Question

How many 4-digit passcodes can be created if each digit can be any number, 0-9?

6,561
10,000
40
5,040

Answer 1

6,561

that's a good number

Answer 2

0 thru 9 is 10 numbers.

Each digit can be 1 of 10 numbers:

Total combinations = 10 x 10 x 10 x 10 = 10,000

Answer: 10,000